Carlos Alcaraz has given an explanation after he was spotted "sniffing" something during his group stage match at the ATP Finals.

After getting off to a losing start on Monday, the world No. 3 redeemed himself and beat Andrey Rublev in his second round-robin tie.

Alcaraz has been carrying an illness while in Turin and took to the court wearing a neon pink nose strip. He was also seen blowing his nose and sniffing a pot during the changeovers.

There were doubts over whether Alcaraz would even take to the court on Wednesday. Since arriving in Turin, the Spaniard had been practising wearing a nasal strip because he had a blocked nose.

He admitted he didn't feel well during his opening match and, on Tuesday, the Spaniard cancelled a practice session after spending just a few minutes on court.

But he returned to action as normal to face Rublev, this time donning the nose strip in competition. It seemed to do the trick - he dazzled the crowd with some of his signature drop shots and secured a 6-3 7-6(8) victory.

The pink bandage wasn't the only thing Alcaraz used to feel better. He also wore vapour rub on his chest for the second match in a row and appeared to be inhaling the fumes from the pot instead of using an inhaler stick.

Asked about the measures he took, the four-time Grand Slam champion said: "Yeah, I know [Nicolas] Jarry wears that thing in the nose. For me, it helped a lot today. I could breathe much better.

"It is something that I'm going to wear more often, I don't know. Right now in the situation that I'm right now, it help a lot.

"I'm pretty sure that in the next match I'm going to wear it. Tomorrow's practice I'm going to wear it, for sure. I felt better. I could recover better between points."

As for what he was sniffing, Alcaraz added: "Yeah, the thing that I sniffed in the changeover, it is for that. It is just to breathe a little bit better. The things between points that I'm doing like that is because of it. It help me a lot to recover and to breathe better."

And Alcaraz will likely take the same measures for his third and final group match on Friday after noticing an improvement compared to his opening tie.

Alcaraz looked out-of-sorts when he suffered a 6-1 7-5 defeat to Casper Ruud at the start of the week and knew he had to turn things around against Rublev. "The match against Casper, it was difficult one for me. I didn't feel well," he explained.

"It doesn't matter. I had to play better feeling the way I felt against Casper. Today I felt almost the same. Probably a little bit better, but not too much.

"Yeah, today I step on the court thinking I have to play better. That's it. Try to forget about I'm not feeling well and focus on I have to play a good tennis, playing good rallies, good shots from the baseline, try to serve better. It's going to be helpful for today's match, the serve.

"I had many options in my mind if I could not feel well on the baseline running. I'm really happy that everything worked today from the baseline. Long rallies. After that, I could recover between points. I'm really grateful and really happy to be able to do it."

The Spaniard still has a chance of making it out of the round-robin stage and into the semi-final but he will likely need to beat recent Paris Masters champion Alexander Zverev to have a shot.